The effects of rubber content and temperature on dynamic fracture toughness of ABS materials have been investigated based on the J-integral and crack opening displacement (COD, delta) concepts by an instrumented Charpy impact test. A multiple specimens R-curve method and stop block technique are used. It is shown that the materials exhibit a different toughness behavior, depending on rubber content and temperature. The resistance against stable crack initiation (J(0.2) or delta(0.2)) increases with increasing rubber content. However, J(0.2) first increased with increasing temperature until reaching the maximum value; after that, it decreases with further increasing the temperature. (C) 2000 John Wiley & Sons, Inc.